Splits a linked list of positive integers into two lists, one of even and one of odd integers. T:O(n) S:O(1)

even_odd_split.py

class Node:
    def __init__(self, value=None, next=None):
        self.value = value
        self.next = next


def print_list(head):
    while head:
        print(head.value, end='->')
        head = head.next
    print()

def 

def even_odd(head):
    if not head:
        return
    odd = None
    even = None
    l1 = head
    while l1:
        if l1.value % 2 == 0:  # even
            if not even:
                even = l1
                l2 = even
            else:
                l2.next = l1
                l2 = l2.next
        else:                  # odd
            if not odd:
                odd = l1
                l3 = odd
            else:
                l3.next = l1
                l3 = l3.next
        l1 = l1.next
    
    if l2: l2.next = None
    if l3: l3.next = None
    return odd, even


head = Node(1, Node(2, Node(3, Node(4, Node(5, Node(6))))))
print_list(head)
odd, even = even_odd(head)
print_list(odd)
print_list(even)